High frequency induction heating and roll forging of metal workpieces



Jan. 19, 1960 v. w. GREEN HIGH FREQUENCY INDUCTION HEATING AND ROLL FORGING OF METAL WORKPIECES Filed Jan. 12, 1959 'FIG. I

FIG. 3

FIG. 4

FIG. 2

. INVENTOR VERNOR WAYNE GREEN FIG.5

ATTORNEY United States Patent HIGH FREQUENCY INDUCTION HEATING AND ROLL FORGING OF METAL WORKPIECES Vernor Wayne Green, Stamford, Conn., assignor to The Taylor-Winfield Corporation, Warren, Ohio, a corporation of Ohio Application January 12, 1959, Serial No. 786,265

11 Claims. (CL 219-75) The present invention relates generally to the art of forming objects or workpieces. More particularly, the invention is directed to the provision of methods and apparatus for the high frequency induction heating and roll forging of metal workpieces where the material is not readily susceptible to known forming operations or where the desired geometry of the formed workpiece cannot be economically produced in accordance with presently known methods and apparatus.

It has long been recognized by those skilled in the art that certain materials and certain shapes of finished workpieces are not adapted to conventional cold forming or forging operations and accordingly various types of hot forming or forging methods have been developed and are now widely practiced. As an example, one such method consists of passing high amperage electrical current through a workpiece to soften and heat the same and then applying suitable pressure to the softened workpiece to gather the same into the final desired shape. This method is known generally by the terminology electric resistance hot upsetting and is illustrated in the patent to Stermon, No. 2,813,194, wherein there is shown apparatus for hot upsetting the opposing edges of a plurality of plates.

Although such prior art forming and forging methods have and are widely employed they are characterized by certain limitations as will be discussed below. One of the most serious limitations of such methods is that certain materials are not readily adapted to be formed or forged thereby and this is particularly true of the very hard and special purpose alloys which are now being developed. Also, such methods are rather slow and are incapable of high rates of production which are necessary for the economical and efficient forming or forging of the finished workpieces. The apparatus employed for completing these methods is very large and expensive due. to the large electrical system and the high force applying system required.

It is therefore the primary or ultimate object of the present invention to provide improved methods and ap: paratus which are capable of rapidly and efiiciently forming or forging metal workpieces or objects of materials and shapes not readily adaptable to other known methods of forming and forging. As an example, the present methods and apparatus may be employed to shape the edges of zirconium plates for use as nuclear fuel elements or to roughly form the edges of plates of special purpose alloys for use as turbine blades. In the latter use of the methods and apparatus of the present invention the properly formed plates would be severed into short sections transversely of the direction of forming or forging and then these individual sections can be machined to their final desired shape.

Another object of the invention is to provide methods and apparatus for the hot forming or forging of metal workpieces which are characterized by their utmost simplicity in construction and operation. In essence, as will be hereinafter more fully explained, the apparatus 2,922,014 Patented J an. 1 9, 1 960 comprises a clamping die for holding a plate-like workpiece adjacent an edge thereof, a high frequency inductor element and a properly contoured forging roll. The inductor element and the forging roll heat and form the edge of the workpiece in a highly efficient manner upon relative movement between the workpiece and the inductor element and forging roll.

A further object of the invention is to provide methods and apparatus of the character above described which are capable of high speed operations to quickly and efficiently form workpieces of materials and shapes which are not adapted to other types of forming or forging operations.

The above, as well as other objects and advantages of the invention, will become more fully apparent upon consideration of the following specification and accompanying drawing wherein there is disclosed several representative embodiments of the invention.

In the drawing:

Figure l is a side view showing high frequency induction heating and roll forging apparatus constructed and employed in accordance with the teachings of the present invention;

Figure 2 is an end sectional view taken along the section line II-II of Figure 1;

Figure 3 is a fragmentary and perspective view of a. properly formed workpiece produced by the apparatus of Figures 1 and 2;

Figure 4 is a partial end perspective view of yet another properly formed workpiece which may be formed according to the methods and apparatus of the present invention; and

Figure 5 is a side view depicting a second embodiment of apparatus of the present invention for forming workpieces constructed in accordance with the present invention.

Referring now to the drawing, and initially to Figures 1-3 thereof, there is shown high frequency induction heating and roll forging apparatus for carrying out the methods of the present invention. This apparatus comprises a pair of opposed clamping dies 10 and 11 which are adapted to forcibly engage the sides of a plate-like workpiece 1.2 adjacent the longitudinally extendingtop edge thereof. The clamping dies 10 and 11 are machined along their upper internal edges to provide outwardly and upwardly extending beveled surfaces 13 which cooperate to define a die portion for confining the softened metal of the workpiece 12 to the desired shape'during forming operations as will be hereinafter more fully ex plained. The clamping dies 10 and 11 are mounted on a suitable stationary base, not shown, for relative transverse sliding movement and conventional actuating equipment, also not shown, would be provided for actuating the clamping dies. The actuating equipment is operative to apply considerable clamping force to the clamping dies 10 and 11 whereby the workpiece is tightly held by the clamping dies against movement in any direction. For reasons which will be hereinafter more fully apparent, the workpiece 12 is accurately positioned within the clamping dies so that only a predetermined edge 14 of the workpieceprojects above the upper surfaces 16 of paratus shown the induction heating assembly and the roll forging assembly are moved across the exposed top edge of the workpiece with'fthe induction heating assembly operative to heat and. soften the edge of the workpiece and the roll forging assembly following immediately thereafter to 'form' or forge the exposed upper edge. of the workpiece to the desired shape.

The induction heating assembly 17 consists of hair pin shaped inductorelement 19 which is fabricated frorn a single loop of current conductive material thereby defin ing a pair of spaced parallel longitudinally extending reaches 20 which are received in nesting relation over the 5,922,014. N: 1 V v p upper edge of the clamped workpiece 12. It should be understood that the teachings of the invention are not limited'to. the provision of a hair pin shaped inductor element since the inductor element may be any of a variety of shapes and; might consist of more than one turn of of the workpiece projecting above the edge of the clamping dies. Thehigh frequency generator 21 is'energized surfaces '13 of theclamping dies; Both the inductorelecurrent conductive material depending upon the shape and volume'of the portion of the metal workpiece to 'be heated as will be apparent to those skilled in the induction heating art. The, upturned ends of the inductor element are connected to a conventional high frequency ence numeral 21. Various high frequency generators are commercially available, such as rotating generators,

'spark gap type generators, oscillating type generators and yacuum tube oscillators, for example, and the generator generator which is designated in the drawing by the referment and the forging'roll move along the upper edge of the workpiece to progressively soften and form the workpiece in a continuous and efiicient manner. It will be notedthatlthe forging roll bears against the upper surfaces 16 of theclamping dies 10 and 11 as the same rolls across the workpiece and that the peripheral die groove in the forging wheel cooperates with the beveled surfaces of the clamping dies todefine an accurate and precise die structure for forming the upper edge of the workpiece. In this mannerit is insured that the finished 21 serves as a source of supply for high frequencycurrent for inductively heating the upper edge of the clamped iworkpiecef The frequency employed will, of course, depend upon the dimensions and typeof material being formed, the volume ,or amount of material along the upper edge of the workpiece being formed and the speed at which the forming operations are completed. These factors are easily calculated and controlled and the best frequency for any given situation can be deterruined either theoretically or empirically as will be underworkpiece will have the same cross section throughout its entire length. r

. Although in the illustrated embodiment of the inven- 'tion' the inductor element and the forging roll are shown as beingmovable across the edge of a stationarily clamped workpiece, thespresent invention, in its broader aspects, is "not limited to this arrangement; In some cases it may be desirable to stationarily mount themductor elementand the forging roll-while moving the stood by those skilled in this particular art. The inductor element 19 is preferably formed of electrolytic copper tubing so that a cooling medium, such as water," can be circulated therethrough.

" The inductor element does not touch the upper edge of the workpiece but nests in spaced relation therewith.

The inductor element and the workpiece form an air coupled transformer with the single turn inductor element serving as the primary and the workpiece serving as the secondary. Upon energization of the high -frequency generator 21 the workpiece will be exposed to an alternating or varying magnetic flux thereby inducting a current which will flow wholly within the mass of the workpiece to cause rapid eddy-current heating of the workpiece. The frequency employed and the shape of the inductor element are such that the secondary current is limited and confined primarily to theupper edge of the workpiece whereby only this portion of the workpiece is heated and softened for subsequent forming.

Mounted immediately behind and adapted to follow clampedworkpiece. In any event, however, the arrangement is such that "relative movement is effected between the clamped workpiece and the inductor element and the forging roll. r r i As mentioned above, it is preferred that the forging roll engage. the upper surfaces 16 of the clamping dies during forming operations so that the edge of the workpiece is accurately formed to the desired shape throughout its entire length. However, if the thickness or the width of the workpiece varies toany considerable extent the forging 'roll will not always be in con- ,tact'with the clamping dies and it may be desirable to .allowlsome'flash to extrude between the, roll and the clamping dies. in' some cases. Such flash could be removed from the workpiece after the forming of the edge thereof if the same is objectionable.

.A1so,,it maybe desirable to preheat the forging wheel prior'tov the commencement of a forming operation. If the forging wheel is initially cold at the start of atomingope'ration it will be heated as it moves across the immediately after the induction heating assembly 17 is the roll forging assembly 18. The roll forging assembly comprises a yoke-like bracket 22 which journals and rotatably supports a forging roll 23. The forging roll 23 is formed from a relatively hard material, preferably 7 nonmagnetic, and is machined to provide adeep die groove 24 around the outer peripheral edge thereof. As herembefore intimated, the roll forging assembly is mounted from a movable carrier and the forgingroll is' adapted for rolling movement across the upper edge of the workpiece. applying means, not shown, for applying a considerable force to the forging roll and hence to the upper edge portion of the workpiece.

-Considering now the preferred operation of the apparatus above described, a workpiece is first positioned within the clamping dies 10 and lland very firmly and rigidly clamped with a predetermined upper edge portion formedto define an Lbeam-like structure. This may be This assembly also comprises pressure heated, and softened edge of the workpiece. This may cause some undesirable variation in the forming of certain shapes and materials. ,,To overcome this problem a the forging, wheel. may' be preheated about its outer periphery to any. desired temperature by meansofan inductor heating element which could be suppliedfrom the high frequency generatorjll'used to supplythe inductor element 19 by providing suitable switching means, also,not shown';, I f.

} -lnrFigure 3', 'of' the drawing there is shown a finished workpiece sanduit willj'be noted that both of the longitudinal edges of] the p'latelike workpiece .have been accomplished, by turning the workpiec'ein the clamping dies, to expose both edges thereof to theinduction heating and roll forging assemblies or, alternatively, by providing a pair 'of induction heating and forging roll assemblies for both side edges of the workpiece while clamping the same intermediate its ends. Zirconium plates can be formed'to the shape shown in Figure 3 of the drawing in a minimum oftime and in a highly ,eflicient manner for sess fuel,elements in.nucleaueactors-i Figure 4'- of the drawing shows another article comprising a body: portion 25 and an enlarged head portion 26 which may be formed according to the teachings of the present invention upon selection of clamping dies and 'a forging roll defining the desired shape. Such an article is formed from plate material and may serve as blanks for turbine blades upon being severed into a plurality of individual sections along axes transverse to the longitudinal axis of the enlarged head portion 26; It should be clearly understood that the invention, in its broader aspects, is not limited to the forming of any particular shape of finished product since obviously any of a variety of articles may be formed depending upon the shapes of the clamping dies and the contour of the forging roll. The methods disclosed are not limited to forming plates or bars. It can be applied equally well to curved strips or bars, to the forming of a flange or enlargement on a disc or to shapes ofany other geometry which can be exposed to a forging roll or segment of a forging roll having any desired shape of peripheral face or die groove. Also, the formed or forged portion need not extend in the same. plane as the plane of the main body portion of the workpiece since proper shaping or contouring of the groove in the forging wheel will direct the formed portion in any practicable angle with respect to the vertical plane of the main body portion of the workpiece.

In some cases, where especially high speeds of operation are desired and/or the volume of material to be formed is relatively large, it may be desirable to provide a plurality of induction heating and roll forging assemblies working in series for accomplishing the forming or forging operations. Such an arrangement is shown in Figure of the drawing where the workpiece St) is clamped between the clamping dies 31 with the upper edge thereof exposed. Mounted above the workpiece and clamping dies in aligned series relation are a first inductor element 32, a first forging roll 33, a second inductor element 34 and a second forging roll 35. The inductor elements are, of course, connected to a high frequency generator and serve to heat and soften the upper edge of the workpiece for forming by the forging rolls. The peripheral surface of the first forging roll is contoured or grooved to roughly shape the upper edge of the workpiece while the second forging roll is contoured and grooved to thereafter form the roughly formed edge of the workpiece to the final desired shape. Of course, the apparatus of Figure 1 could be used in multiple step forming operations by making a plurality of passes with the induction heating and forging roll assemblies and changing the forging roll between passes. However, it is preferred that the tandem or series arrangement utilizing a plurality of induction heating and roll forging assemblies be employed where extensive multiple forming or forging operations are contemplated.

It should thus be apparent that I have accomplished the objects initially set forth by providing improved methods and apparatus for the high frequency induction heating and roll forging of metal workpieces. Although several representative embodiments of the invention have been disclosed it should be understood that the same are intended to be illustrative only since many changes may be made therein without departing from the clear teachings of the invention. Accordingly, reference should be had to the following appended claims in determining the true scope and intent of the present invention.

I claim:

1. The method of forming the edge of a workpiece to a desired shape which comprises the steps of clamping said workpiece with an edge thereof exposed, generating a high frequency alternating magnetic field, concentrating said high frequency alternating magnetic field in a portion of said edge of said workpiece to rapidly heat and soften the same, engaging said edge of said workpiece with a forging roll having its outer periphery contoured to said desired shape, applying an upsetting pressure to said forging roll and said workpiece, and moving said workpiece and said high frequency alternating magnetic field and said forging roll relative to each other to progressively soften and form said edge of said workpiece to said desired shape.

2. The method of forming the edge of a workpiece to a desired shape which comprises the steps of clamping said workpiece with an edge thereof exposed, generating a high frequency alternating magnetic field, concentrating said high frequency alternating magnetic field in a portion of said edge of said workpiece to rapidly heat and soften the same, engaging said edge of said workpiece immediately adjacent said portion of said edge of said workpiece with a forging roll having its outer periphery contoured to said desired shape, applying upsetting pressure to said forging roll and said workpiece, and moving said high frequency alternating magnetic field and said forging roll relative to said edge of said workpiece whereby said edge of said workpiece is progressively and continuously softened and formed to said desired shape by said high frequency alternating magnetic field and said forging roll.

3. The method of forming the edge of a workpiece to a desired shape which comprises the steps of clamping said workpiece with an edge thereof exposed, generating a first high frequency alternating magnetic field in a first portion of said edge of said workpiece to rapidly heat and soften the same, engaging said edge of said workpiece behind said first portion with a first forging roll having its outer periphery contoured roughly to said desired shape, generating a second high frequency alternating magnetic field in a second portion of said edge of said workpiece spaced behind said first high frequency alternating magnetic field and said first forging roll, engaging said workpiece with a second forging roll positioned behind said second high frequency alternating magnetic field and having its outer periphery contoured to said desired shape, applying upsetting pressure to said forging rolls and said workpiece, and progressively and continuously forming said workpiece to said desired shape by effecting relative movement between said workpiece and said high frequency alternating magnetic fields and said forging rolls.

4. Apparatus for forming the edge of a workpiece which comprises a pair of clamping dies for firmly clamping said workpiece with the edge thereof exposed, a high frequency inductor heating element received in nesting relation over a portion of said exposed edge of said workpiece, a forging roll mounted to the rear of and immediately adjacent said high frequency inductor element adapted to engage said exposed edge of said workpiece, said forging roll having a groove in its outer periphery, said groove having a shape complementary to the desired shape to be formed on said edge of said workpiece and defining a die, means for applying upsetting pressure to said forging roll, and means for effecting relative movement between said workpiece and said inductor element and said forging roll for progressively softening and forming said edge of said workpiece.

5. Apparatus according to claim 4 further characterized in that said clamping dies have relieved portions defining die openings on the inner surfaces thereof, said forging roll being of greater width than said edge of said workpiece, said forging roll being adapted to roll on said clamping dies in straddling relation with respect to said edge of said workpiece, and said groove in said forging roll and said die openings in said clamping dies cooperating to form said edge of said workpiece.

6. Apparatus for forming the edge of a workpiece to a desired shape which comprises clamping means for firmly clamping said workpiece with the edge thereof exposed, a high frequency inductor heating element received over a portion of said exposed edge of said workpiece for rapidly heating and softening the same, a forging roll positioned to the rear of'said' high frequency inductor heating element adapted to engage said exposed edge of said workpiece, said forging roll having its outer periphery-contoured to said desired shape of s'aidedge of said workpiece, means for applying upsetting pressure to said forging roll, and means for effecting relative movement between said workpiece and said high frequency inductor heating element andsaid forging roll for progressively and continuously softening and forming said edge of said workpiece.

, 7. Apparatus according to claim 6 further characterized in that said forging roll is wider than said edge of said workpiece, and said forging r011 being adapted to roll on said clamping means in straddling relation with respect to said edge of said workpiece. 8, Apparatus according to claim 6 further characterized in that said claimping means comprises a pair of clamping dies engaging opposite sides of said workpiece adjacent said edge thereof, said clamping dies having relieved portions on the inner surfacesthereof defining die openings, and said die openings and said forging roll cooperating in forming said workpiece to said desired shape.

9. App'aratusaccording to claim 6 further character-v ized in that said forging roll has a groove therein com: plementary to said desired shape of said'edge of said workpiece, and said groove forming said'edge' ofsaid workpiece asthe same rolls thereacros'sa i 10. Apparatus according to claim 6 further characterized in that said means for effecting relative movement References Cited in the file of this patent UNITED STATES PATENTS 2,464,658 Stivin 4---. Mar. 15, 1949 2,813,194 Stermon Nov. 12, 19 57 FOREIGN PATENTS 475,931 Germany May 6, 1929 

